This invention relates to a new restriction enzyme and to a process for producing the same. More particularly, it relates to a new restriction enzyme, Mfl I, produced by microorganisms belonging to the genus Microbacterium, and also relates to a process for producing the same.
Restriction enzymes are endonucleases that are capable of recognizing a specific sequence of bases on a deoxyribonucleic acid (DNA) molecule and of cleaving the double-stranded DNA chain at specific sites. As a result of progress in molecular genetics, biochemistry and related sciences, it is now clear that DNA is the carrier of genetic information, and restriction endonucleases have been extensively used for various purposes (clarification of genetic diseases, mass production of genetic materials based on genetic engineering, etc.). About 100 kinds of endonucleases have so far been isolated from many microorganisms, each being identified by the specific base sequence it recognizes and by the mode of cleavage.
Of these, Xho II, produced by Xanthomonas holcicola (ATCC 13461), is known to be a restriction endonuclease which recognizes the base sequence as shown below and cleaves the DNA chain at the arrow-marked positions, EQU 5'--Pu.dwnarw.GATCPy--3' EQU 3'--PyCTAG.uparw.Pu--5'
Xho II, however, has problems for its industrial application. These include its low production yield from Xanthomonas holcicola, and unavoidable contamination with difficult-to-remove Xho I (C.dwnarw.TCGAG). In addition, cleavage takes place at the same positions as above even when the A residue in the above recognition sequence has a methyl substituent.